Vascular filter system

ABSTRACT

A removable vascular filter system for blocking micro- and macro-emboli while allowing the continued perfusion of blood comprises a filter membrane positioned on a guidewire, wherein a free end of the membrane sits tightly against the guidewire when the filter membrane is in a collapsed state and wherein the filter has a means for deploying the filter membrane to assume a position substantially normal to the longitudinal axis of the guidewire. The filter membrane is comprised of a fine mesh material which has a pore size capable of blocking emboli while allowing continued blood flow, a preferred embodiment of which comprises regularly spaced, laser-formed holes, and in which the membrane has a scalloped proximal profile.

FIELD OF THE INVENTION

The present invention relates to the treatment of vascular diseaseduring either surgery or percutaneous angioplasty and stenting. Moreparticularly, the invention relates to a system that reduces macro- andmicro-embolization during the treatment of vascular stenosis.

BACKGROUND OF THE INVENTION

A variety of surgical and non-surgical procedures have been developedfor removing obstructions from blood vessels. Balloon angioplastyutilizes a balloon-tipped catheter which may be inserted within astenosed region of the blood vessel. By inflation of the balloon, thestenosed region is dilated. Surgery involves either removing the plaquefrom the artery or attaching a graft to the artery so as to bypass theobstructing plaque. Other techniques, such as atherectomy, have alsobeen proposed. In atherectomy, a rotating blade is used to shave plaquefrom an arterial wall.

One problem common with all of these techniques is the accidentalrelease of portions of the plaque or thrombus, resulting in emboli whichcan lodge elsewhere in the vascular system. Such emboli are extremelydangerous to the patient, frequently causing severe impairment of thedistal circulatory bed. Depending upon the vessel being treated, thismay result in stroke, myocardial infarction or limb ischemia.

During a postoperative period vascular filters are used, when there is aperceived risk of the patient encountering a pulmonary embolus resultingfrom the lots generated at the surgical site. As a typical use ofvascular filters, the filter is mounted in the vena cava to catch largeemboli passing from the surgical site to the lungs.

Permanent implantation of a filter is often medically undesirable, yetit has been done because vascular filters are implanted in patientsprimarily in response to potentially life threatening situations.Accordingly, permanent implantation of a vascular filter is oftenaccepted.

Nonetheless, avoid permanent implantation, it would be desirable toprovide an apparatus and method for preventing embolization associatedwith conventional surgery and angioplasty procedures. In particular, itwould be desirable to provide a device which could be located within thevascular system to collect and retrieve portions of plaque and thrombuswhich have dislodged during the surgery or angioplasty procedure.

OBJECT OF THE INVENTION

This invention provides a vascular filter system for reducing macro- andmicro-embolization.

It also provides a vascular filter system which is readily removablefrom the vascular system of a patient when the filter is no longerneeded.

Further, it provides a vascular filter system having a configurationwhich does not require hooks to penetrate and grip the blood vesselwalls, so that filter deployment results in less blood vessel injury.

Further the invention provides a vascular filter system of very lowprofile which is delivered along a guidewire and can be used in smallvessels.

The invention will become more readily apparent from the descriptionbelow.

SUMMARY OF THE INVENTION

The present invention generally relates to a vascular filter systemuseful in the treatment of vascular disease, in particular, apercutaneous angioplasty and stenting system useful, for example, in thetreatment of carotid arterial stenoses. Macro- and micro-embolizationoccurs during such angioplasties, which increases the risk of stroke.The system of the present invention is useful in preventing such risk.This system is also useful in any procedure in which embolization is arisk.

The vascular filter system of the present invention decreases embolicevents while allowing distal tissue perfusion. The filter isincorporated into a guidewire which is used during the entire procedure,from first crossing of a lesion through deploying a stent. In oneembodiment, the filter consists of a thin membrane attached to theguidewire and supported by fine metal spines. Attachment of filter toguidewire allows membrane expansion, to provide a firm fit inside theartery. Also, the system allows collapse of the filter membrane at theend of the procedure, so that it fits tightly against the guidewire andis withdrawn through the guide catheter.

In another embodiment, the membrane rests upon or is attached to abasket-like structure, at least one end of which is attached to theguidewire. The membrane has a pore size such that blood flow is notimpeded when the filter membrane is expanded, but through which micro-and macro-emboli are blocked. Expansion of the filter membrane is aidedby the forward flow of blood against the filter. The filter designresults in a very low profile so that the initial go crossing of thelesion via the guidewire is minimally traumatic. Also, small diameterand narrow profile facilitate use of the device in smaller or largerarteries with minimal or no obstruction of blood flow.

Further embodiments of this filter membrane and its deployment systemare provided without departing from the general nature of the guidewirebased system. Among those are various modifications of the folding madeto the filter membrane, and its configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

The above advantages of the invention will be apparent uponconsideration of the following detailed description, taken inconjunction with the accompanying drawings. In these drawings, referencecharacters refer to like parts throughout.

FIG. 1 is a lateral, partial cross-sectional view of the distal end of aguidewire of one embodiment of the invention, with the filter membranein a collapsed position;

FIG. 2 is a lateral, partial cross-sectional view of the distal end of aguidewire of FIG. 1 with the filter membrane in an expanded, deployedposition;

FIG. 3 is a proximal end-on view of the filter membrane shown in FIG. 2;

FIG. 4 is a lateral, partial cross-sectional view of another embodimentof the invention;

FIG. 5A is a lateral, partial cross-sectional view of a furtherembodiment of the invention;

FIG. 5B is a lateral, partial cross-sectional view of the embodiment ofthe invention shown in FIG. 5A with the filter membrane in an expanded,deployed position;

FIG. 6 is a partial cross-sectional view of a control handle for theinvention;

FIG. 7 is a partial cross-sectional view of another embodiment of theinvention;

FIG. 8 is a partial cross-sectional view of an embodiment of theinvention in which the filter membrane has curved supports;

FIG. 9 is a partial cross-sectional view of yet another embodiment ofthe invention in which the filter membrane has a spiral wire;

FIG. 10 is a top cross-sectional view of the embodiment of the inventionshown in FIG. 9;

FIG. 11 is a partial cross-sectional view of another embodiment of theinvention having inflatable support spines;

FIGS. 12 and 13 represent partial cross-sectional views of anotherembodiment of the invention in collapsed and deployed positions,respectively;

FIG. 14 is a lateral, partial cross-sectional view of one embodiment ofthe invention with the filter membrane in an open position;

FIG. 15 is a lateral, partial cross-sectional view of the embodiment ofthe invention in FIG. 14 with the sheath closed;

FIG. 16 is a schematic representation of a portion of a filter membraneaccording to the invention;

FIG. 17 is a lateral view of a core wire useful according to theinvention;

FIG. 18 is a cross-sectional view across line 18—18 of a portion of thecore wire of FIG. 17;

FIG. 19 is a lateral, cross-sectional view of an alternative basketstructure for the embodiment of FIG. 14;

FIG. 20 is a lateral, partial cross-sectional view of another embodimentof the invention;

FIG. 21 is a lateral, partial cross-sectional view of a furtherembodiment of the invention;

FIG. 22 is a schematic, partial cross-sectional view of anotherembodiment of the invention where the distal section of the filterbasket is inverted;

FIG. 23 is a schematic, partially cross-sectional view of the embodimentshown in FIG. 22 where the filter basket is collapsed; and

FIGS. 24, 25, 26 and 27 are schematic views of other modifications ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a vascular filter system for use inpercutaneous angioplasty and stenting and provides for the prevention ofdistal embolism during endovascular procedures. Further, the filtersystem of the invention allows for distal perfusion while preventingembolization.

The system comprises a thin, perforated filter membrane which is capableof blocking emboli and which is attached to the distal end of aguidewire. In one embodiment the system uses thin fibers which aremoveable and are attached to or encapsulated by the filter membrane todeploy and/or collapse the filter membrane. The invention alsocontemplates the use of metal spines or inflatable spines attached tothe filter membrane to deploy the filter membrane. The fibers or spinescan also be attached to a moveable core which is slidable within theguidewire and is used to deploy and collapse the filter membrane.

The filter membrane deploys in an umbrella-like fashion with theunattached edge of the membrane moving upward, i.e., distally, andoutward until it is in firm contact with an artery wall. When the filtermembrane is deployed, it spans the cross-sectional area of the vessellumen being treated for a stenosis such as carotid stenosis, or anothercondition likely to produce emboli.

In another, preferred embodiment of the invention, a thin, flexible,perforated membrane is supported by four or more supports that form adistally extending basket. At least one end of the basket is attached tothe guidewire, and the other, slidable end can be moved to cause themembrane to open or close.

The invention can be appreciated by reference to the drawings. FIG. 1illustrates a lateral, cross-sectional view of a distal end of aguidewire 10 with a filter membrane 20 attached thereto. FIG. 1 showsguidewire 10 with a shapeable, tapered soft tip 15 at its extreme distalend which provides flexibility and maneuverability to guidewire 10. Thefilter membrane in FIG. 1 is in a collapsed position. Filter membrane 20has a fixed portion 24 which is movably attached to guidewire 10, andfilter membrane 20 lies adjacent guidewire 10 proximal to fixed portion24 when filter membrane 20 is in the collapsed state. A moveable core 40runs through a center lumen 11 of guidewire 10 and preferably extendsdistally a short distance beyond fixed portion 24 of filter membrane 20.Deploying wires or fibers 30 are each firmly attached at one end 27 tomoveable core 40 distal to fixed portion 21 of filter membrane 20. Thedeploying fibers 30 are attached at their other ends to filter membrane20 at attachment points 22.

Collapsing fibers 35 are each firmly attached at one end 12 to theportion of moveable core wire 40 which is interior to filter membrane 20when it is in the collapsed state. Collapsing fibers 35 are eachattached at their other end 13 to filter membrane 20 at attachmentpoints 22. Accordingly, collapsing fibers 35 lie interior to filtermembrane 20 when filter membrane 20 is in the collapsed state.

Filter membrane 20 is deployed when the operator pulls moveable core 40proximally through the interior of guidewire 10. Prior to retraction ofmoveable core 40, deploying fibers 30 are sufficiently relaxed so as notto create any tension at filter membrane attachment points 22. Uponretraction of moveable core 40, tension is created in deploying fibers30.

There will preferably be from 2 to 6 evenly-spaced deploying fibers 30and collapsing fibers 35, with 3 or 4 such fibers 30, 35 being mostpreferred. The deploying fibers 30 and collapsing fibers 35 can be madeof any flexible, medically acceptable material, including stainlesssteel, nitinol, another metal or metallic alloy, a non-metallicsubstance such as graphite, or a suitable polymer. In addition,guidewire 10 and moveable core 40 can be made from similar materials.Typically, guidewire 10 has an external diameter of from about 0.014 in.to about 0.035 in., a wall thickness between about 0.002 in. to about0.010 in., and a length between about 25 cm to about 300 cm. Also,moveable core 40 could have a diameter of from about 0.003 in. to about0.010 in. and a length of from about 30 cm to about 350 cm.

FIG. 2 illustrates the filter device of the invention in a deployedposition on the inside of an artery wall 60. Moveable core 40 is in aretracted state, i.e., pulled proximally through the interior ofguidewire 10. Tension is created in deploying fibers 30, and filtermembrane 20 extends to a deployed position, where the outer edge 14 offilter membrane 20 contacts artery wall 60. In this deployed position,collapsing fibers 35 are in a relaxed state and extend from filtermembrane attachment points 22 to fixed attachment points 28 on moveablecore 40.

The flow of blood in FIG. 2 is toward the distal end of guidewire 10. Assuch, the force of the flow of blood pushed on deployed filter membrane20 and helps to maintain filter membrane 20 in the deployed position.

For withdrawal of guidewire 10 and the filter device, filter membrane 20is collapsed so that it sits tightly against guidewire 10. This isaccomplished by extending moveable core 40 distally through guidewire10, thus relaxing deploying fibers 30 and creating tension in collapsingfibers 35. The tension in collapsing fibers 35 collapses the filtermembrane 20, allowing it to fit tightly against guidewire 10 in therecess 16, as depicted in FIG. 1.

FIG. 3 illustrates the filter device of the invention from a distal endview in FIG. 2, with filter membrane 20 deployed. Guidewire 10 iscentrally located, and structural wires 50 are seen extending fromguidewire 10 to the outer edge 14 of filter membrane 20. These wires 50provide structural integrity and rigidity to filter membrane 20. FIG. 3depicts four, evenly-spaced structural wires 50, but there can be moreor less structural wires 50. Preferably there are from two to sixstructural wires 50. The wires 50 may preferably be made of stainlesssteel or another medically acceptable metal or alloy.

Filter membrane 20 of the invention is preferably a mesh such as thatdepicted in FIG. 3. The mesh should have pores of a size sufficient toblock and capture any micro- and macro-emboli which may flow downstreamfrom the site where the stenosis is being treated, but large enough suchthat blood flow is not impeded. The mesh used in the filter device ofthe invention can have a pore size less than 300 microns, preferablyfrom about 50 to about 150 microns. Moreover, the distance fromguidewire 10 to free ends 22 allows a firm fit between filter membrane20 and artery wall 60. The diameter of filter membrane 20 will bedirectly related to the artery being treated, with typical diametersranging from less than about 2 mm to about 40 mm, most preferably fromabout 2 mm to about 20 mm.

The membrane can be comprised of fabric or non-fabric meshes, such asthose used in known hemodialysis filters or heart-lung bypass machinefilters. Suitable materials include polymers or physiologicallyacceptable metals or alloys.

In alternative embodiments of the invention seen in FIGS. 4, 5A and 5B,filter membrane 20 is suspended between from two to eight, preferablyfrom four to eight, thin metal wires 51 which serve as spines for filtermembrane 20. Wires 51 may be comprised of stainless steel or anothermetallic alloy, nitinol, or another shape-memory material. Wires 51 areconstructed so that they assume a 90° angle with guidewire 10 when theyare in an unconstrained state. This will result in expansion of thefilter membrane 20 to a position normal to guidewire 10. A set of thinfibers 17 are attached at attachment points 18 to filter membrane outeredge 14 and are used to collapse filter membrane 20.

FIG. 4 shows an embodiment of this invention in which metal wires 51 areallowed to regain their unconstrained 90° angle state by use of amoveable core 40 that runs through guidewire 10. Prior to retraction ofmoveable core 40, fibers 17 b are sufficiently tensed so as to restrainwires 51. Upon retraction of moveable core 40, tension in fibers 17 isreleased and wires 51 are allowed to revert to their relaxed shape,which will result in expansion of filter membrane 20 to a positionnormal to guidewire 10.

FIGS. 5A and 5B show an embodiment of the invention wherein wires 51 arerestrained by fibers 17 that run through guidewire 10 and that arecontrolled at a remote location. In FIG. 5A, there is sufficient tensionin fibers 17 to maintain wires 51 in a constrained position. In FIG. 5B,tension in fibers 17 has been relaxed such that wires 51 are allowed torevert to their relaxed shape, which will result in expansion of filtermembrane 20 to a position normal to guidewire 10.

FIG. 6 depicts a control handle especially suitable for the embodimentof the invention shown in FIGS. 5A and 5B. The proximal end 32 ofguidewire 10 is rotatably attached to handle 33, such that rotationcauses handle 33 to move relative to proximal guidewire end 32. Forexample, handle 33 may have threads 34 which engage threads 35 onguidewire proximal end 32. Fibers 17 attached to filter membrane 20 aresecured in a base 36 of handle 33. Then, as handle 33 is turned, thefibers 17 move distally or proximally to open or close filter membrane20.

As handle 31 is turned clockwise in the direction of arrow A and fibers17 are allowed to move distally in the direction of arrow C, the tensionon the filter membrane fibers 17 decreases, and wires 51 are allowed toassume their natural 90° angle with respect to the guidewire, resultingin opening of filter membrane 20. Similarly, when handle 33 is turnedcounterclockwise is the direction of arrow D, the tension on filterfibers 17 increases, causing filter membrane 20 to collapse tightlyagainst guidewire 10. Of course, the direction of turn of handle 33 asdiscussed above can be reversed, as long as threads 34, 35 are properlyformed to allow appropriate movement of handle 33 relative to guidewireproximal end 32.

In yet another embodiment of the invention shown in FIG. 11, filtermembrane 20 can be supported by inflatable spines 135 supporting thefilter membrane 20. Spines 135 supporting the filter membrane 20 arefrom two to six hollow plastic tubes which are inflatable using, forexample, a standard balloon angioplasty inflation device or endoflatorin fluid connection through channel 137 with spines 135. Inflation ofspines 135 causes them to become rigid and deploys filter membrane 20.The underside of the filter membrane is attached to very thin fibers 17which are attached to moveable core 40 inside hollow guidewire 10.Filter membrane 20 is collapsed by deflating the spines 135 andwithdrawing the moveable core 40 in the direction of arrow E until themembrane 20 fits tightly against guidewire 10.

A catheter-based configuration is also possible, as shown in FIG. 7. Inthis design the guidewire and filter catheter are two separatecomponents. The filter catheter has an entry hole for the guidewire andthe guidewire exits out the end of the filter catheter. The filtercatheter could be designed to accommodate a variety of guidewire sizes,most commonly a 0.014 inch guidewire. The advantages of this design arethat a variety of guidewires may be used; the lesion is crossed with theguidewire prior to crossing with the filter catheter; the filtercatheter is removed from the artery without removing the guidewire; andthe filter catheter is made smaller.

In the embodiment of the invention shown in FIG. 7, a catheter 101comprises a longitudinally extending lumen 103, which as an annularrecess 105 adjacent the distal end of catheter 101. Positioned withinrecess 105 is a filter 107 comprised of structural wires 109 and afilter membrane 111. The distal end of each, of wires 109 is attached atpoint 113 in recess 105. Fibers 117 extend from the proximal ends 119 ofwires 109 proximally to a control means such as described in FIG. 6.

Catheter 101 contains guidewire port 125 located proximal to recess 105.It is intended that in use the distal portion 128 of a guidewire 127will be threaded into the distal end 129 of catheter 101 and out throughport 125.

Alternately, (not shown here) a catheter 101 could comprise alongitudinally extending lumen and a shorter tracking lumen that extendsfrom distal end 129 to a point proximal to recess 105. The distal end ofguidewire 127 would then be threaded into the distal opening of thetracking lumen and out the proximal end of the tracking lumen.

Spiral or curved structural wires may be used to deploy the filtermembrane instead of straight wires. FIG. 8 illustrates the use of fourcurved wires 120. The angulation of the filter attachment point of wires120 relative to their guidewire attachment has the effect of wrappingthe filter fabric around the guidewire in the undeployed state. Thisleads to a lower profile for the undeployed filter.

FIGS. 9 and 10 illustrate the use of a single spiral structural wire 130which is attached to the filter 107. As tension fiber 131 is released,wire 130 unwinds and deploys filter 107 in a conical configuration. Thisconfiguration has the simplicity of using a single wire and, when thetension on fiber 131 is increased, allows filter 107 to be wrapped verytightly around the guidewire shaft 131, resulting in filter 107 having alow profile in its undeployed state.

Another modification shown in FIGS. 12 and 13 comprises a retractablesheath 140 at the distal end of guidewire 142 which covers filtermembrane 144 in the collapsed state. The distal portion of sheath 140 isaffixed to guidewire tip 146; tip 146 is affixed to the distal end ofmoveable core 148. This prevents an edge 150 of filter membrane 144 frombecoming entangled in an artery or guide catheter during withdrawal froma patient.

More specifically, when guidewire 142 with tapered tip 146 is insertedpercutaneously into a patient, sheath 140 covers collapsed filtermembrane 144. After the filter membrane is determined (usually byfluoroscopy) to be in proper position, moveable core 148 is pusheddistally to cause sheath 140 to “release” from filter membrane 144,which has spines 152. This causes filter membrane 144 to deploy, asshown in FIG. 13.

FIG. 14 illustrates a lateral, cross-sectional view of a distal end of aguidewire 160 with a filter membrane 170 attached thereto. FIG. 14 showsguidewire 160 with a shapeable soft (sometimes referred to as “floppy”)tip 162 at its extreme distal end, to provide flexibility andmaneuverability to guidewire 160. The filter membrane in FIG. 14 is inan open position.

Guidewire 160 comprises a core wire 164, which extends into floppy tip162, and sheath 166. Filter membrane 170 is supported by a basket 169comprising two or more filter basket wires 168, having distal ends 172and proximal end 174. The distal ends 172 of basket wires 168 arefixedly attached to core wire 164 by distal radiopaque marker or crimpband 176, and the proximal ends 174 of basket wires 168 are attached toproximal radiopaque marker or crimp band 178, which is slidable overcore wire 164, optionally with a polymeric (such as polyimide) ormetallic sleeve between core wire 164 and proximal ends 174. Optionally,and preferably, proximal marker 178 is fixedly attached to core wire164, and distal marker 176, with a polymeric or metallic sleeve, isslidable over core wire 164.

A sheath member 180 is attached to the distal end of sheath 166, sheathmember 180 having a lumen 182 with a diameter and length sufficient toreceive or slide over proximal marker 178. Sheath 166 and sheath member180 can be either separate bonded pieces or a continuous, integralstructure. Sheath 166 and sheath member 180 are each made from lowfriction polymeric material, preferably polytetrafluoroethylene,polyethylene, nylon, or polyurethane.

Filter membrane 170 can comprise a number of different metallic ornonmetallic permeable membranes having sufficient porosity to facilitateblood flow, but having sufficiently small openings to capture emboli.Filter membrane 170 must be affixed at least at its distal portion 184to core wire 164 and/or basket wire distal ends 172 and, optionally, tobasket wires 168. The remainder of filter membrane 170 can be unattachedor, preferably, attached to basket wires 168, such as by a suitableadhesive. Preferably basket wires 168 are encapsulated in membrane 170.

Basket 169 can be somewhat cylindrical in its middle with conicallytapered proximal and distal portions. Alternatively, basket 169 can beslightly spherical, optionally with a cylindrical flat middle portion.Preferably basket 169 is from about 5 to about 40 mm in length and fromabout 2 to about 30 mm, or from about 2 to about 20 mm in diameter, atits widest.

The proximal end of sheath 180 is attached to control handle orguidewire torquer 186. Control handle 186 has an opening 188, for corewire 164 so that sheath 180 can move slidably over core wire 164. Forexample, when sheath 180 is moved distally toward basket wires 168,filter membrane 170 collapses. Also, there may be instances where sheath180 will be removed proximally so that other catheters or cardiovascularappliances can be introduced over core wire 164. Control handle 186,which functions as a torque device, also primarily functions to locksheath 180 to core wire 164 during insertion.

There are a number of known, commercially available guidewire torquersthat may be modified to function as control handle 186. Modificationincludes, but is not limited to, providing a slightly larger centrallumen.

In FIG. 15 sheath 166 and sheath member 180 are shown advanced distallyso that basket wires 168 and filter member 170 are collapsed againstcore wire 164. The distal end 192 of sheath member 180 may optionally beslightly tapered to provide a better profile for insertion.

In a preferred embodiment of the invention, as shown in FIG. 16, filtermembrane 170 comprises a polymeric material such as polyurethane orsilicone elastomer that has laser-drilled holes 190. Such holes 190, apattern for which can be seen in FIG. 16, are preferably only on theconical portion of filter membrane 170. The holes 190 could be fromabout 50 to 300 μm in diameter. The vertical separation of holes 190 canbe from 1.2 to 1.4 times the hole diameter and the center-to-centerdiameter of holes 190 can be from about 1.4 to 1.6 times the holediameter. In a preferred embodiment, the vertical and horizontal spacingof the holes is such that the center-to-center spacing of the holes isfrom about 1.2 to 2.0 times the hole diameter. Preferably, the open areaof the holes represents from about 10 to 50 percent, more preferablyfrom about 15% to 40%, of the filter surface.

Basket wires 168 are made of a suitable, physiologically acceptablematerial. Stainless steel or nitinol are preferred, although titanium orother metal alloys could be used.

Core wire 164 can be seen better in FIG. 17, where the proximal andmiddle portions 200 and 202 are substantially uniform in diameter, andthen the distal portion 204 tapers to an end point 206. In fact, distalportion 204 could taper uniformly or, more preferably, non-uniformly, asshown in FIG. 17. Typically, core wire 164 is from about 250 to 300 cmin length, with an initial diameter of from about 0.009 in. to 0.038in., preferably from about 0.014 in. to 0.018 in. Distal section 204 istypically from about 8 to 10 cm in. total, with a diameter that tapersto from about 0.001 in. to 0.005 in. Core wire 164 may optionally have athin polymeric coating 207 for friction reduction. Preferably end point206 is a solid, squat cylinder, as shown in FIGS. 17 and 18.

Floppy tip 162 preferably comprises a radiopaque helical spring 210 thatis fixedly attached, e.g., by welding, brazing, or soldering, to endpoint 206 and, optionally, attachment point 208. Optionally spring coil210 may have a polymeric or lubricious coating 212.

FIG. 19 represents yet another alternate design. Basket wires 220 aresubstantially helical in shape. Filter member 222 covers or encompassesthe distal portion of basket wires 220. Proximal and distal portions ofbasket wires 220 are secured by proximal radiopaque marker or crimp band224 and distal radiopaque marker or crimp band 226, respectively.Markers 224 and 226 are fixed or slidable on core wire 228 as describedabove. Preferably there are from 4 to 8 basket wires 220, each with arotation of from about 45° to 360°.

Additional embodiments of the invention can be seen in FIGS. 20 and 21.The schematic representation in FIG. 20 depicts a filter membrane 280supported by strut wires 282. The distal ends 284 of strut wires 282 areattached to the distal portion of a tubular member 286. A movable corewire 290 extends through a lumen 292 in tubular member 286 to distalfloppy section sections 294, where a helical spring coil 296 surroundsthe distal portion 298 of core wire 290 and is attached to end point300. An attachment point 302 of weld or solder at the proximal portionof spring coil 296 where the distal portion 304 of sheath member 306 isalso attached to core wire 290. The lumen 308 of sheath member 306 islarge enough so that as core wire 290 is pulled proximally, or tubularmember 286 is advanced distally, the distal ends 284 of strut wires 282move into lumen 308 and collapse filter membrane 280.

Moveable core wire 250 of the structure shown in FIG. 21 comprises afloppy tip 252 where a helical spring coil 254 encompasses the distalportion 256 of core wire 250. A basket wire structure component of twoor more basket wires 258 supports a filter membrane 260 on the distalportion 262 of the basket structure. Distal ends 264 of the basket wires258 are encompassed by a radiopaque market or crimp band 266 that isattached to core wire 250 and/or spring coil 254. The proximal ends 268of basket wires 258 are attached to the distal portion of a sheath 270that surrounds core wire 250. Sheath 270 moves slidably over core wire250 so that when sheath 270 is pulled proximally into core wire 250,filter membrane 260 collapses.

In FIG. 22 a basket 320 comprised of from 4 to 8 strut wires 322 issecured by a distal fixed grommet 324 and a proximal slidable grommet326. Grommet 326 is slidable over core wire 328. Filter membrane 330 isattached to or arranged upon basket 320, with the proximal section 332of the membrane 390 being open to flow, represented by arrows 334. Thedistal portion 336 of membrane 330 forms a conical shape 340 thatextends proximally. The filter could be deployed by, for example, asheath or a tube fixed to the proximal slidable crimp band 336. Thisdesign is optimized for perfusion and emboli collection. For example, asmore emboli is collected, it tends to collect in non-filter areas,leaving the pores open for perfusion.

Membrane 330 preferably has holes only in the distal section 336/340,which holes are arranged as described above. It is believed that undernormal, (substantially laminar) flow conditions debris or emboli 342will tend to collect in annular recesses 344.

To close and capture emboli, as shown in FIG. 23, slidable grommet 326is moved proximally to collapse basket 320 and membrane 336. This can beaccomplished with, for example, sheath 350 or a fixed tubular member orother apparatus that is preferably slidable over the core wire.

Various modifications of the current invention are described in theappended FIGS. 24 through 27. As seen in FIGS. 24 and 25, a slightmodification of the profile p of the filter membrane 500 will result ineasier folding of the membrane inwardly either prior to or subsequent tocapture of embolic material. That is, as seen in FIG. 24, the membraneis provided with a scallops S forming profile P. As seen in FIG. 25, theprofile P contains more curves C, shaped somewhat like a bat's wings.The scallop shapes “S”, as seen in FIGS. 24 and 25 are intended to beshapes in which the unfurled profile of the filter membrane is such thatthere are alternate longer and shorter sections around the circumferenceof the stent in the shape of a scallop. In either event however, thisreduced leading edge profile for the filter membrane 500 allows foreasier folding of the membrane subsequent to its collection of embolicmaterial. The membrane 500 folds more readily because at its distal ends501 folds, there is less material to be placed in-close juxtaposition.Accordingly, this type of fold will enable the material to be captured,and yet also provide for more ready disposition of the membrane.

The membrane 500 can be cut in such a profile by standard techniques,including among other things, laser cutting, as is discussed above.

As seen in the embodiment of FIG. 26, a balloon 601 is incorporatedoutside the basket element 600 of the filter membrane 550 so thatelement 600 “floats” inside the balloon 600. In this embodiment, theballoon 601 is placed outside of the filter mechanism 550. The balloon601 is then laser drilled, creating larger holes for entrance of embolicarticles. A basket is thus formed “inside” the balloon. The balloon isthen seated as a basket only at its distal end. In this fashion, thefilter element is incorporated into the profile of a balloon and so isfurther able to provide for embolic capture.

As seen in FIG. 27, struts 700 are placed intermediate the struts 702used to fold the membrane 701 inward during collapse. These strutsprovide for greater stability of the membrane 701 during emplacement inthe artery. For even further stability, there could be placed smallerstruts (not shown) bridging these fingers.

It is to be understood that any of the embodiments described herein canbe made by laser cutting the membrane mechanism possibly even into aself expanding hypo tube. Further, the mechanism can be made by dippingthe device into a bath containing the polymer of the membrane. In thisfashion, the dimensional depth of the bath can be adjusted to providefor optimal performance of the membrane material.

The wires, membrane, and other materials of this embodiment areconsistent with those described above.

The preceding specific embodiments are illustrative of the practice ofthe invention. It is to be understood, however, that other expedientsknown to those skilled in the art or disclosed herein, may be employedwithout departing from the spirit of the invention or the scope of theappended claims.

We claim:
 1. A removable vascular filter system comprising: a guidewirehaving distal and proximal ends, a filter membrane having a distalportion and a proximal free end portion, wherein said distal portion ispivotably attached to the guidewire near said distal end of theguidewire and wherein the proximal free end portion is substantiallyparallel to the guidewire in its collapsed state and wherein said freeend portion has a generally scalloped shape; and deploying means forcausing the filter membrane to assume a position substantially normal tothe longitudinal axis of the guidewire.
 2. The vascular filter system ofclaim 1, whereby the deploying means comprises a control mechanism atthe proximal end of the guidewire operatively connected to the filter.3. The vascular filter system of claim 1, wherein the filter membrane iscomprised of a porous mesh, and the scalloped shape is comprised ofstraight or rounded sections.
 4. The vascular filter system of claim 3,wherein the pore size of the porous mesh is from about 20 to about 300microns.
 5. A removable vascular filter system comprising: a guidewirehaving distal and proximal portions and defined by a longitudinal axis,wherein there is a recess in the distal portion, the recess havingdistal and proximal ends, a filter membrane having an inner portion anda free end portion, wherein the inner portion is attached to theguidewire near the distal end of the guidewire recess and wherein thefree end portion is positioned in the recess when the filter membrane isin a collapsed state, and wherein the filter membrane in an unstressedposition assumes a position substantially normal to the longitudinalaxis of the guidewire; means for collapsing the filter membrane from adeployed state to a collapsed state; and a network of struts comprisinga deploying mechanism, said struts having alternating longer and shorterlengths and arranged circumferentially about said longitudinal axis.